1. Field of the Invention
The invention relates to a safety device for an actuating system for roller shutters or sliding barriers, the actuating system which incorporates it and the operating method used in it. In particular it relates to an obstacle-sensing protection device. For the sake of simplicity of the description, reference will be made solely to actuating systems for roller shutters, it being understood that the invention may also be applied to automated systems for gates, curtains, external shutters, sliding barriers, doors, garage entrances and the like.
2. Description of the Related Art
In actuating systems for roller shutters, the torque supplied by the electric motor during the movement is not constant over the entire travel path of the roller shutter (opening and/or closing), but varies according to the instantaneous requirement. This is due to the variation in the forces at play and in particular to the variation in the weight of the roller shutter which, during movement of the latter, stresses the motor in a varying manner (gradually increases during the downward movement and gradually decreases during the upward movement). As a result the motor increases or decreases gradually the torque produced in order to keep the speed of the roller shutter more or less constant.
The actuating systems for roller shutters incorporate obstacle-sensing devices in order to intervene immediately, usually stopping the shutter and reversing for a short travel the direction of movement of the motor, in the event of accidental impact with persons or objects.
The obstacle-sensing devices may be of the mechanical or electronic type. The first type generally make use of a mechanical play in order to activate or deactivate a switch which causes stoppage of the motor, see, for example, EP 0 497 711, EP 0 552 459 and FR 2 721 652. The second type—see FIG. 1—generally use the technique of measuring (for example by means of an encoder) a physical parameter (ζ) relating to the operation of the actuating system, denoted here by ζ and called main parameter, in correspondence with a series of positions φn of the roller shutter along its travel path (n=the number of samples) in order to obtain actual analog values ζ(φk). Here and below the dependency on φk for a parameter indicates that the parameter is acquired in real time and in correspondence with the k-th position, while the generic subscript n in φn for ζ(φn) is used to indicate genetically the acquisition in real time for all the n positions, namely a profile of ζ. After sampling, the values ζ(φn) are digitally converted into digital values ζM(φn) (the subscript M indicates here and below an acquired and memorized value) and are stored (or “mapped”) in an ordered manner to form a profile M.
Another advantageous technique is described in the application PCT/EP 0 668 183 in the name of the Applicant. Here the measurement method implemented in the actuating system is able to monitor and map directly the mechanical parameters of the blind and not only the electrical parameters of the motor, namely it is possible to control the force imparted by or onto the roller shutter even when die motor is at a standstill. The “mapping” operation preferably requires two stored profiles, i.e. one for the opening movement and one for the closing movement (they are not necessarily the same).
Usually the values refer ζ(φn) refer to the electric current, to the electric power, to the speed or to the torque produced by the electric motor or to the resisting torque which acts on the roller shutter and/or the motor. Below the function ζ will indicate these parameters or similar electrical and/or mechanical parameters, preferably the driving torque required to obtain a desired profile for the movement of the roller shutter.
It should be noted that the first mapping M or a new mapping of an actuating system must be performed by specialised personnel during the course of a specific programming procedure. In the known systems a complete mapping M is performed with the first operation during installation where the roller shutter is moved from one end-of-travel position to the other one (and vice versa) and then remains valid permanently (or until a new programming/installation cycle is performed).
The profile M is regarded by the system as a reference and/or normal use profile. During the movement of the roller shutter, the values ζM(φk) of the profile M are compared, in real time, with the respective instantaneous values ζ(φk), in order to detect any anomaly with respect to the stored profile M.
A series of phenomena, for example structural “micro-phenomena” which are difficult to predict, such as vibrations and resonances of the structure or the sliding systems, have the effect that an invariable profile M for all the operations is not optimal. In practice it is best to take into account a “background noise” which is superimposed on the profile M and allow for suitable margins of intervention.
Therefore, a tolerance range W is calculated around the profile M, this range comprising values ζW(φk)|inf and ζW(φk)|sup where the subscripts “sup” and “inf” indicate the upper and lower range values, respectively, by adding or subtracting a tolerance threshold S (or maximum deviation value) to/from the values ζM(φk).
The calculation operation for each point is ζW(φk)|inf=ζM(φk)−S and ζW(φk)|sup=ζM(φk)+S, with S being a fixed value.
For example, in FIG. 1, the measured value ζ(φk)|1(1≦k≦n) would be a permitted value, while ζ(φk)|2 would activate the protection system. Another example, if the mapped value ζM(φk) were 50 and a tolerance threshold S (or deviation value) equivalent to 20% of ζM(φk) is assumed, activation of the protection system would be obtained for ζ(φk)<ζW(φk)|inf=40 or ζ(φk)>ζW(φk)|sup=60. All the variations which may occur between the first operation and all the following operations are thus concentrated in the tolerance (or indifference) range W.
These systems may, however, may be improved.
In order to avoid false responses it is necessary for die value S of the tolerance threshold to be sufficiently wide. However, activation of the obstacle-sensing protection system is ensured only when an obstacle produces a detected value ζ(φk) falling outside the range W.
Since the range W is also a range of insensitivity/indifference to obstacles, too large a deviation S may also undermine safety because it widens the range W excessively.
In the case where the mapped parameter ζM(φn) is the torque, the tolerance threshold S is proportional to the (impact) force which acts on (or must be withstood by) the obstacle before the activation of the obstacle-sensing protection system reverses the movement of the motor. In some cases, as for example in the case of shutters for shops (or garage entrances), where the weight involved is considerable, the force to which the obstacle could be exposed may however be excessive.
For this reason, an efficient obstacle-sensing protection device must be characterized by very small tolerance threshold values S.
Moreover, there are phenomena, such as wear of the structure, loss of efficiency by the balancing systems (springs) or climatic (seasonal) changes which produce a slow, but gradual change in the values measured ζ(φn).
Therefore the values ζM(φn) and the corresponding values ζ(φn) measured in real time gradually diverge from each other, something which over time may result in the range W being exceeded in one or more positions φk and increasingly frequent false responses/interventions.